Percussion drill bit for large holes



April 28, 1959 J. A. H JALSTEN Y 2,884,227

PERCUSION DRILL BIT FOR LARGE HOLES Filed June 27, 1956 2 Sheets-Sheet 1INVENTOR MQJ M ATTORNEYS April 28, 1959 J. A. HJALSTEN 2,334,227

. PERCUSSION DRILL BIT FOR LARGE HOLES File d Jun 27, 1956 r z SheetS--Sheet 2 INVENTOR ATTORNEY 5 PERCUSSION DRILL BIT FOR LARGE HOLES JohnAnders Hjiilsten, Sandviken, Sweden, assignor to Sandvikens JernverksAktiebolag, Sandviken, Sweden, a corporation of Sweden Application June27, 1956, Serial No. 594,290

2 Claims. (Cl. 255-64) This invention relates generally to drill bits,and more particularly to percussion drill bits for drilling large holesin rock'and other hard surfaces.

An object of the invention is to provide a drill bit which will drilllarge holes in rock by a one-step operation when provided with asatisfactory drill feed.

Another object of the invention is to provide a drill bit whichfacilitates the drilling of large holes in rock by use of percussionenergy without unnecessarily crushing the rock chips produced.

:A more specific object of my invention is to provide a drillbit'adapted to chip off pieces of: rock of such size thartheymayileasily be. removed from-the percussionarea and the drill hole.

Still another object of the invention is to provide effective means forthe removal of the chipped material from the drilled hole. A furtherobject is to provide a drill bit having means for detaching the variouscutting elements to allow for interchangeability or substitution ofparts whereby drilling of various sizes of holes may be accomplished andeasier maintenance of the tool may be effected.

These and other features of the invention will be more apparent from astudy of the following specification when considered in conjunction withthe accompanying drawings, in which:

Fig. 1 shows a perspective view of a drill bit in accordance with theinvention;

Fig. 2 shows an elevation sectional view of the bit along line 2--2 ofFig. 3;

Fig. 3 shows a plan view of the bit; and

Figs. 4 and 5 are elevational and plan views of one modification of theinner cutting bit body.

Referring now to Fig. l, the body 1 of the drill bit containsprojections 2 peripherally arranged about the cutting area and adaptedto receive outer cutting inserts 3, formed from a suitable hard metalmaterial, such as one or more metal carbides and a binder. By hard metalis here and below meant a sintered product, consisting of one or morecarbides, for example WC and/or other hard materials together with oneor more binding metals, as cobalt and/or other metals in the iron groupof the periodical system. The cutting inserts 3 are preferably brazed tothe drill bit, but other suitable securing means, such as clamping,screwing, or welding, may be utilized as desired. While the cuttinginserts 3 are shown in the drawings to be circularly arranged, it isalso possible to arrange the elements in other configurations, such asan elliptical arrangement for example. The direction of the cuttingedges is shown to be radial, but it is apparent that the elements may bearranged obliquely or tangentially if desired.

Centrally arranged within the drill body 1 and removably secured theretois the inner bit body 4 to which are secured by brazing or othersuitable means the inner cutting inserts 5. While the number of cuttingelements shown in the drawings is six, it is obvious that the number ofelements may be varied as desired. Similarly the orientation of thecutting edges 5 with respect tothe outer cutting inserts 3 may be variedas desired.

As shown in Figs. 2 and 4 the inner bit body is provided with screwthreads 6 adapted to cooperate with the threaded bore 7 in the main bitbodyl to rigidly secure the inner bit body therein.

The inner cutting inserts 5 are usually in the same plane as the outercutting inserts 3, although the inner edges may be positioned in frontof the plane of the outer cutting edges to reduce wear of the outercutting inserts. For special working conditions the bit may bemanufactured so that the plane of the'inner edges will be positionedbehind the plane of the outer cutting edges. As shown in Fig. l, theinner cutting inserts 5 are spaced from the outer cutting inserts 3 bythe flat surface 8 of the drill bit body. The minimum distance betweenof this construction, and in combination with the longil tudinal grooves9 in the outer surface of the main bitv body, the chipped pieces of rockor stone may passoutwardly from the central portion of the cutting areaand subsequently may be removed from the drilled hole. v -In v order toaid in this removal of crushed rock. from. the, drilled hole, a flushingmedium maylbe'applied pressure-through the "bit to the 'cuttingareathrough'p'assages 10 in the bit body 1 or through passage 11 in theinner bit body 4. Thus it may be seen that the chipped pieces of rockwill not be caught between the inner and outer cutting inserts and willreadily be washed from the drilled bore.

It should be mentioned that the grooves 9' extend between the outercutting inserts 3 from the surface 8 longitudinally of the drill bitbody, although it is of course possible to form the grooves intoangular, spiral or curved paths.

In the embodiment as shown in Fig. 2, the outer cutting inserts 3 aresupported in the projections of the main bit body by the retaining ring12 mounted transversely to the longitudinal axis of the bit and securedthereto by suitable securing means, such as by brazing. This retainingring 12 serves not only to support the outer cutting inserts when theyare brazed to the associated projections, but also to support theprojections against oblique stresses during subsequent drilling,handling and transportation of the tool.

The grooves 9 in the outer surface of the main bit body thus extendradially outwardly from recesses 9 in the support ring and are inclinedsomewhere between 10 and 50 with the vertical. As shown in the alternateembodiment of Fig. 4, grooves 13 may be placed in the outer surface ofthe inner bit 4 to further aid in the flushing operation.

The drill bit body 1 is provided with a threaded bore 14 at the lowerportion thereof whereby the drill bit may be secured to the drill rod15.

During the drilling operation, relatively large chips are produced andby means of the surface 8 in the cutting area of the drill incombination with the grooves 9, 9' and 13 in the bit, no furthercrushing occurs and an effective use of the percussion energy ispresented. As mentioned above, the smallest space between the inner andouter cutting inserts is approximately equal to the length of each ofthe outer cutting inserts. The outer diameter of the drill bit 1 ischosen for the drilling of larger holes, for example somewhere betweenand mm., but larger or smaller diameter holes may be produced asdesired. The distance between the inner and outer cutting inserts is onthe order of 12 to 20 mm., or in especial cases more.

While in accordance with the provisions of the statutes,

r. Ice Patented Apr. 28, 1959 I have illustrated and described the bestform of embodiment of my invention-known to me, it will be apparent tothose skilled in the artthat changes may be made in the form of theapparatus described without departing from the spirit of my invention asset forth in the appended claims.

.I claim:

1. A percussion drill bit for drilling large holes in rock or similarsubstances comprising a cylindrical main bit body having a cutting endand a drill rod securing end, said main bit body having a fiat endsurface at the cutting end thereof and a plurality of equally-spacedperipherally-arranged projections axially projecting from said flat endsurface, each of said projections having an outer cutting bit mountedtherein, a cutting insert retaining ring secured to said fiat endsurface of the main bit body in contiguous engagement with a portion ofthe innermost surfaces of said outer cutting inserts, said main bit bodyhaving a central longitudinal bore extending therethrough, an inner bitbody screw-threadably mounted within said bore and having a tubular endportion axially projecting from said flat end surface, a plurality ofequally-spaced inner cutting bits axially projecting from the extremityof said inner bit body tubular end portion, said outer cutting insertsbeing concentrically arranged with respect to said inner cuttinginserts, said inner and outer cutting inserts each having cutting edgessubstantially normal to the axis of said main bit body, the minimumradial distance between said inner and outer cutting inserts beingsubstantially equal to the maximum length of the cutting edge of saidouter inserts, said main bit body having longitudinal grooves on theouter periphery thereof extending between said main body axialprojections and said insert retaining ring having recesses in the uppersurface thereof in alignment with said longitudinal grooves, said innerbit body having a fluid conductive passage extending longitudinallytherethrough and said main bit body having a fluid passage therein whichterminates at one end in an opening in the main body flat end surfaceintermediate said main body projections and said inner bit body and atthe other end in communication with said main body longitudinal boreintermediate the drill rod securing end and the inner bit body, wherebyparticles of drilled material may be readily removed from the annularspace intermediate said inner and outer cutting inserts by theintroduction of pressure fluid into the main body longitudinal bore fromthe drill securing end of the main bit body.

2. A percussion drill bit as defined in claim 1 wherein the minimumradial distance between the inner and outer cutting inserts is greaterthan 12 millimeters.

References Cited in the file of this patent UNITED STATES PATENTS1,785,405 Candee et al. Dec. 16, 1930 1,813,375 Wright et al. July 7,1931 2,282,596 Wise et al. May 12, 1942 2,358,052 Brown Sept. 12, 19442,502,128 Curtis Mar. 28, 1950 2,807,443 Wyman ..e.. Sept. 24, 11957

